Electromagnetic deflection generator



Aug. 9; 1949. G. c. szlKLAl ELECTROMAGNETIC DEFLECTION GENERATOR Filed March 14, 1945 2 Sheets-Sheet 2 HIJ g TO EFL EC T/O/V VOA/E 7- NVENTOR.

Alllll Arron/ver Patented Aug. 9, 1949 ELECTROMAGNETC DEFLEGTION GENERA'IOB George C. Szklai, Princeton, N, J., .lsslgllol -t9 VRadio Corporation ci` America, a corporation Application March .1.4, 1945, .Serial 'ffli? 12 Claims. CL

1 This invention relates to an improvement in deection generators for de ectinga cathode `ray ,beam in cathode ray tube. More particularly, `the invention relates to a system for generating the required current and voltage kvariations `for electromagnetically .deilecting a cathode 4ray .beam- Eletromasneti deflection 0f a cathode' ray beam is frequently employed in apparatus using .cathode ray tubes vparticrllarly y.Where the vdeflec- -tion frequency remains substantially constant. .Such a situation exists in television equipment where the rate of deection and the deflection kfrequency of the cathode ray beam in both the horizontal and the rvertieal fliretions are main- .tained- Substantiallv ilxed- .For .elettromagnetically delecting a cathode ray beam Wherethe :raie of deflection is unferrm, it 11S necessari t0 ycause the flux to alter its density in a Alinear manner. Accordingly, this requires ka -li ,change in the arnountofcurrentthat ls-per to dow through the winding of the electroma netic deflection yoke since thorium; produced b y .the yoke is `substantlally in d lrect proportion to :the amount of current in the winding of tricyclic throughout its normal range o f current variation The yoke is highly inductive,andas a result ,the voltage Aapplied tol the terminals of vthe `B'Qle Winding must be Ainaintained substantially ,throughout the deflectioninterval. Dnder these .conditiona the ,rate of change ,0f ,the currfent and the corresponding retesf @harige or afuxfwill be uniform and constant.

Vario-11s -cirutarraneementshave been devised .for sitromaenetieallyfsssotins asathode ray i beam. and moet circultsbave, vin therast, included blocking oscillators for controlling a discharge tube to plOduce @desired-voltage ,variation arieh, vin turn, fis lapplied to gan output deioction tube for producing the ldesir-ed current verano-ns. 'Such fcil., ion :systems Often b@- come ratherinvolved a usually entailthe-use considerable number of-tubes. Furthermore, previous systems, in which 'a llesser number -Gf tubes are used, are not Wholly satisfactory in i rthat the operating frequency, theamplitude -of .deflection and thelinearitypf cleection-arenot unrelated, thus makingfit neoessaryto v adjust-al1 three of these,parametersssheuldzit becomes-etessary to adjust anyone.

Conventional v.electrorria'gnetic deflection veircuits are also frequentlyobjectionable vfrom 4 the ,standpoint ofestablity, .and require, regularly recurrius synchronizing ...impulses t0 .rre/.enit Aerraticpper. .tion of .th deleeilensenetalvr- ,.Eur

` tnermore, previously used deflection systems couldnt readily'b controlled in frequency by the application o fa relatively V.low potential to the system thereby 'making it difi'icult to apply automatic frequency control potentialsto the deflection generator. l

The present invention comprises a simple and reliable system for `producinfg current variations ior electromagnetically` def1ecting a cathode ray beam in avcatho'de ray tube. VThe present invention includes ess entiadl'yonlytwo" tubes, one of which operates as Aan'oscillator and Ithe other operates as the usual damping or inverted tube. 1n the present invention both the .amplitude of de iiection and thefrequency or rate of deection may beindependentlycontrolled without in any way affecting the other. Furthermore, the

frequency of o eration of the present invention may also be cok rolled vby the ,application of a relatively srnxalllv control potential so that automatic frequency'control'rnayreadily be applied tothe pr-,esentilflyention The system shown and Ydescribed herein is, ls'oresponsive ,to synchroniz- 5,5 eraticnmey be maleta;

lectivo .generator in `ithipll 1? for adjusting boththe amplitudeof deection and ing impulses of Yrelatively lovv amplitude, thus making it possible r4to synchronizethe frequency of operation of thedeetll generator from a v series of available or received `synchronizing impulses.

. ne purpose ci the Npresent inventionresides in the provision ofadehecting generatorfor electromagneticallydeilecting the, cathode ray beam, the generator being simple incineration, and involving a ',relativelylsniall number .of essential ele- '.ments.

Another purposepf the 'present invention resides-in the rovislonof an electromagnetic derovisions are made the frequency of defiectiorif,.each of these adjustments being .entirely inlependento 4the other.

Still another purpose .of the'present invention rresides inthe provision of an electromagnetic Vdeflection generator which ``is responsive to syn- ,ohronizillg ,impulsesof relatively low intensity.

A stillhfurther purpose o f the present invention resides in the Infor/1i,sion of Van A electromagnetic Vde iiectio'n V`generator in Which the frequency of operation 'of theA generator may be controlled withinprescribed limits byV the 'application .of a relatively lovv,direct4 currentpotential to the oscillator tube `of tljie deflection generator.

`Still another purpose ofthe present invention resides in the' provision of anelectrcmagnetic deflectiongenerator in Tlvvh theffrequency of oprl 'constant 1with 4prac- 3 tically no deviation from the prescribed frequency of operation through the use of a simple tuned circuit associated With the oscillator tube.

A further purpose of the present inventio-n resides in the provision of a simple and efficient electromagnetic deflection system which requires a relatively small amount of driving power.

Various other purposes and advantages of the present invention will become more apparent to those skilled in the art from the following detailed description particularly when'considered in connection with the drawings wherein like reference numbers represent lke parts and wherein;

Figure l represents one form of the present invention;

Figures 2 and 3 show curves representing the current and voltage variations occurring at certain points in the deflection system; l

Figure 4 shows a curve relating operating freduency to applied control voltage; and,

Figure 5 shows a rnodied form of the present invention.

Referring now to the drawings and particularly to Figure l, there isshown an oscillator tube it and an inverted or damp-ing tube I2. Oscillator tube Ill includes at least a cathode i2, a control electrode i4, a screen grid electrode i6 and an anode I8. This tube should preferably be in the form of a beam power amplier tube of a type similar to the 6L6 tube and should be capable of dissipating considerable power to a screen grid electrode. The damping tube l2 also includes a cathode 28, a control electrode 22, a screen grid electrode 24 and an anode 2t. This tube should also preferably be in the form of a beam power tube.

The deflection generator also includes transformer te which comprises three windings t2, 313 and 35. The winding 32 may be considered as a secondary winding since the terminals 38 o this winding are connected to the deflection yoke (not shown) The winding 36 is included in the plate or anode circuit of tube Iii and one end of the winding 36 is connected to the anode i8 of tube I while the other end of the winding it is connected to terminal 4t (to which a source of positive potential is applied) by way of the amplitude control resistor 42.- A condenser 44 is connected between this Side of the winding it and a point of xed potential or ground. The winding 34 is for feed-back purposes and applies the necessary blocking potential to the screen grid electrode l5 of the oscillator tube i9. One

`end of the winding `34 is therefore connected to a screen grid electrode I6 of tube ID while the other end of the winding 34 is connected to a point of xed potential or ground by way of a low `frequency controlv resistor 46. The negative terminal ofthe source of potential is applied to terminal 43 which is connected to the point of fixed potential or ground.

In order that current may flow Ythrough the plate winding 36, the cathode I2 'of tube lil is connected to ground by wayof cathode resistor 5B while, in the form of the invention shown in Figure 1, the control electrode I4 of the oscillator tube ID may be connected to ground by way of grid resistor 52.

The plate or anode of the damping tube I2, which is essential for linearizing the deection of the cathode ray beam, is connected directly to the source of positive potentialvwhile the cathode 2i? of the damping tube is connected directly7 to the anode I8 of tube I Il. The control electrode of tube I2 is connected to the anode i8 and to the cathode 29 by two series networks each including a parallel connected resistance and condenser. The parallelly connected resistance 54 and condenser 56, together with the parallelly connected resistance 58 of the condenser control the potential variations that are to affect the control electrode 22 for controlling the impedance of the damping tube l2 in a manner such as to compensate for the lack of linearity in the characteristics in the oscillator tube Iii. The screen grid electrode 24 of the damping tube I2 is connected to a movable contact of a potentiometer t2 and the resistance element of the potentiometer is connected between the positive and negative -terminals of the potential source. Accordingly, by adjusting the movable contact along the resistance element or the potentiometer t2, the positive potential applied to a screen grid electrode 24 is controllable. A condenser 64 is connected between the screen grid electrode '24 and a point of fixed potential.

In describing the operation of the circuit ars rangement shown in Figure l, it should rst be pointed out that the transformer 33 operates both as the oscillation transformer and the output transformer. Furthermore, the oscillator tube lil operates as an electron switch for connecting the yoke inductance through the plate transformer winding 36 to the applied source of potential. When the oscillator tube I@ is in a conducting condition electronic current flows from ground through the cathode resistor 5S, from cathode I2 to anode I8, through the plate winding 36, and to the source of posit-ive potential 4t. This current increases according to the parameters of the circuit and in a substantially vlinear manner until the potential drop across resistance 46 which is applied to the screen grid electrode i6 of the oscillator is suincient to block the oscillator tube from operation.

It will be observed that the yfeed-back winding 34 responds to the flow of current through the plate Winding 36. At the instant that the oscillator tube Il! is blocked, energy stored in the deflection yoke, by reason of its inductance, will discharge in an oscillatory fashion through its distributed capacity until the potential of the lower end of the plate winding 3i; becomes negative with respect to the opposite end of that winding. At this time, a negative potential is applied to the cathode 2t of tube i2 and a posi- 1tiie potential is applied to the anode of that As soon as this condition occurs, the damping tube I 2 begins to conduct and the electronic current flow during the interval is from the cathode '2t to the plate 25 of tube i2, through the amplitude control resistance 42, the plate winding tu,

YVand back to the cathode 20. The wave form of the current which flows during the interval of conductivity of the damping tube I2 is dependent `A current through the damping tube I2, aside from increasing the efficiency of the system, also materially improves the linearity of deflection by compensating for the non-linearity of the oscillator tube, provided the circuit parameters aserly chosen. Y y Y For a predetermined time after blocking of the oscillator tube, the current passed bythe damping tube flows through the plate winding 36. This current diminishes and nally the electronic current in the plate winding 36 reverses since the current supplied by the cathode i2 :of the voscillator tube Iii exceeds the amount of current passed by the damping tube i2.V During a portion of the operating cycle, electronic current ows through both the oscillating tube-and the damping tube with the current through the oscillating tube increasing'somewhatl linearly to a predetermined maximum. At'theend-of the cycle, the oscillating tube lliJ is again blocked by the application of a negative 'impulse `of potential to the screen grid I6 of that tube and the cycle, begins again.r n

This cyclical operation of the circuit continues and its frequency may be adjusted by altering the value of the resistance :46. A .decrease in the size of this resistance is effective to decrease theV frequency of operation while an increase in the resistance 46 increases the frequency vof operation. This cyclic operation and the resulting generation of deflection .currents are continued even in the absence of any synchronizing impulses applied to the .control electrode I4.

Reference is now made to Figure. 2 where the vsociated with the .control electrode '22 ere'propv cathodeA current passed by the oscillator tube Y I0 and the plate current of the damping tube i2 are related. The current lthrough the oscillator tube is represented by the curveV 10 while the damping tube current isrepresented bycurve l2. The differential current of these two tubes .is represented by the. curve 14 which is, in fact,

the current vwhich flowsthrough Vthe winding 36. It will .be observed vthat the. wave form of neither the oscillator northe damping tube is linear yet the net current of these two tubes is quite linear and it is this net current that is effective, through the use of the transformer, in determining the linearity of Y deflection of the cathode ray beam. Figure 3 .shows the voltage that is present at thev screen grid electrode I6 of the oscillator tube l0. It will be observed that this voltage is positive. (approximately 10D volts) during the entire working cycle of .the

oscillator tube andthat va relatively high negative potential is present in the instant that the oscillator is blocked. VThis negative potential may be as high as 1,060 volts or more and it is for this reason that the screen grid kelectrode should be capable of dissipating `considerable energy. If

Since the feedback, voltage Vfor controlling the .oscillator tube i6 Vis applied` to the screen grid electrode I6, the .control electrode I4 is available for synchronizing purposes. Due tothe high transconductance of the control electrode i4 it has been found that avery small synchronizing signal or impulse is effective to synchronize or .lock the oscillator. synchronizing signals of low .intensity and of negative polarity may, therefore.- be applied to terminal TB in order to synchronze the deiiection generator with aV source .trol electrode potential.

Afor television purposes.

of recurring impulses. lUnder these conditions Voperation and the potential applied to the'control electrode. If, for example, the frequency control resistance 46 chosen such thatthe oscillator operates at approximately 16,000 cycles per second, then this frequency of operation may be increased or decreased within prescribed limits by the application of an appropriate direct `current potential to the control `electrozzle 14.

YThis variation in frequency is of the order of about 3% for each one volt change `in-'the con- The potential of the control electrode I4V should not, however, be made more than aboutr 3.5 volts negative since the application of a negative potential in excessth-ereof tends to render the Adefiecton generator unstable. A yvariation in potential 'from approximately 3 volts negative to 2 or more volts positive is lentirely feasible and the resulting change in frequency is well within Vlthe range necessary to permit the use kof automatic frequency control circuits, if desired. Circuit arrangements Vfor producing the desired automatic frequency control potentials for controlling the operating'frequency of the deflection generator are shown and` described, for example, in the patent to Guanella, No. 2,231,998, issued on February 1j8, 19,41, andin the patent toWe-n-dt', No. 2,339,536, issued on .January 18, 1944.

As pointed outabove, the cathode of the damping .tube i2 may be driven several thousand volts .should .be maintained at a 'minimum since such capacity electrically appears directly across the outputV transformer 36 and will affect or extend the `return time which should'be kept short, espe.- cially if the deflection generator is to be used y The use `of a floating transformer or the use of chokes is wellA within the province of one skilled in the art, However, such expediences are not always desirable and a circuit arrangement such as shown in Figure 5, representing a modification ofthe Subd ect invention, maybe employed whereby the cathode of the dampingtube is operated at or near ground potential. In general, this circuit arrangement vis somewhat similar to the circuit shown in Figure 1 except that the damping tube i2 of' Figure 5 is connected across the gridfor-feed-backwinding 34 instead of across the plate winding 36 as 4in Figure l. Since the energy contained in the deflection yoke is reiiectedv into the transformer 3U, this energy'may be controlled by connecting thel damping tube l2 across either of'the windings. 1 In Figure 5, the winding 36 carries the plate current of the oscillator tube only while the current through the damping tube l2 is permitted to flow through the feed-back winding 34.' The diiTerentiaLor net current, of the two tubes is still, however, effective to control the rate of deflection since both these windings 36 and 34 are associated on the same transformer 30 and are electromagnetically coupled to the secondary winding 32 to which the deection yoke is connected.

As a further means for vaccurately determining or controlling the frequency of operation of the deflection generator a tuned circuit such as the .inductance 8U andA a capacitance 82 may be employed and connected in circuit with the control electrode I@ of the oscillator tube Il] as shown inFigure 5. If the coarse frequency control,

including the resistance ll, is adjusted so that the oscillator will operate at near the resonant frequency of the inductance Sil and the condenser'82, thenthe deflection generator will function at the resonant frequency of this circuit. The accuracy with which the value of the resistance 48 must be set is determined by the Q of the resonant circuit. Although this resonant circuit is disclosed as applied to the circuit shown of Figure 5, such an arrangement is also applicable to the circuit shown in Figure 1 and synchronizing impulses or direct current potentials may be utilized to control the frequency of operation ofthe circuit arrangement shown in Figure 5.

The tuned circuit including inductance 8i] and capacitance 82 may also be used inconjunction with synchronizing impulses or automatic frequency control potentials. Where it is desired to so control or lock" the frequency of operation of the deiiection generator, the tuned circuit may be isolated from ground insofar as direct current potentials are concerned by the condenser 8f3 which is relatively large, as compared with the condenser 82. Automatic frequency control potentials or synchronizing `impulses may then be applied between ground and the terminal 86.

The circuit shown in Figure is actually as effective for producing linear deflections of a cathode ray beam as is the circuit of Figure 1 and similarly the amplitude or size control and the frequency control of the generator are independently adjusted. The circuit of Figure 5 may, however, produce slight oscillatory ripples in the return trace, but this is not objectionable in most instances unless the pulse that occurs during this interval is to be used in associated circuits.

4 Through the use of either of the systems shown in Figure 1 or Figure 5 it is evident that a simple and effective deflection generator has been produced which may be used for electromagnetically deiecting a cathode ray beam and in which the deflection of the beam is substantially linear throughout its entire deflection stroke. As pointed out above, the circuit arrangements shown and described herein have the advantage that the amplitude of deflection, the frequency of operation, and the linearity of deflection may be independently controlled. Furthermore the system may be readily locked in operation at a desired frequency through'the use of applied synch-ro- .nizing linpulses or it may be stabilized or conftrolled by the application of a direct current potential. A tuned resonant circuit with or Without the inclusion. of a crystal may also beV used for 8 definitely fixing the'frequency of operation. Ii the tuned circuit, when used, is not too sharply resonant, automatic frequency control potentials or synchronizing impulses may also be used to control the frequency over a range of several percent as shown in Figure 5.

It is to be understood that the present circuit arrangements, although developed primarily for television use, may be well applied to any electrical equipment where electromagnetic deflection of a cathode ray beam is employed.

I claim:

1. An oscillator for producing current variations of substantially sawtooth waveform comprising an electron discharge tube having at least a cathode, a control electrode, a screen electrode and an anode, a first inductance connected between the anode. of;A saldi tube and the positive terminal of a source of potential, the negative terminal of which is connected to a point of fixed potential, meansfor connecting the cathode of said discharge tube to the point of fixed potential, a second inductance connected between the screen electrode and the point of fixed potential, said first and second inductances being electromagnetlcally coupled, a damping tube connected across said first inductance, and means for applying a variable direct current potential to the control electrcde of the electron discharge tube to control the operating frequency of the oscillator.

2. An oscillator for producing current variations of substantially sawtooth waveform comprising an oscillator tube having at least a cathode, a control electrode, a screen electrode and an anode, a first and a second inductance element electromagnetically coupled to each other, means for connecting the first inductance between the anode oi said oscillator tube and a source of positive potential, means for connecting said second inductance between the screen electrode and a point of xed potential, means for connecting the cathode of said oscillator tube to the point of iixedY potential, a damping tube connected across said second inductance, means to control the transconductance of said damping tube, and means for applying a variable direct current potential to the control electrode of said oscillator to control' the frequency of operation of the oscillator.

'3. A deec'tion generator for producing current variations of substantially sawtooth Waveform comprising an oscillator tube having at least a cathode, a control electrode, a screen electrode and an anode, aV rst inductance connected between the anode and the positive terminal of a source of potential, means for connecting the cathode to the negative terminal of the source of potential, a second inductance, means for connecting said. second inductance between said screen electrode and the negative terminal of the source of potential, said rst and second inductances being electromagnetically coupled, a damping tube connected across one of said inductances, and means whereby low potential synchronizing impulses of negative polarity may be applied to the control electrode of said tube to control the frequency of operation of the deflection tube.

4. An oscillator for producing current variations of substantially sawtooth waveform comprising an electron Vdischarge tube having at least a cathode, a control electrode, a screen electrode and an anode, a first inductance connected between the anode of said tube and the positive terminal of a sourcefof potential, the negative terminal of whichis connected toa point of fixed potential, means for connecting the cathode of said discharge tube to the point, of fixed potential, a second. inductance connected between Lthe screen electrode and the point `of ixed potential, said first and second inductances being electromagnetieally couple'eha damping tube connected across said first inductance, means lfor controlling the conductivity of said' damping tube, and means for applying synchronizing impulses to the control electrode of the electron discharge tube to control `the Yoperating frequency ,of the oscillator.

5. An oscillator for producing current variations of substantially sawtooth waveform comprising an oscillator tube having at least acathode, a control electrode, a screen electrode and an anode, first and second inductance elements elec tromagnetically coupled to each other, means for connecting the first inductance between the anode of said oscillator tube and a source of positive potential, means for connecting said second inductance between the screen electrode and a point of iixed potential, means for connecting the cathode of said voscillator tube to the point of fixed potential, a damping tube connected across said second inductance, means to control the transconductance of said damping tube, and means for applying synchronizing impulses to the control electrode of said oscillator to control the frequency of operation of the oscillator.

6. An oscillator for producing current variations of substantially sawtooth waveform comprising an oscillator tube having at least a cathode, a control electrode, a screen electrode and an anode, a rst inductance connected between the anode of said tube and the positive terminal of a source of potential, means for connecting the cathode of said tube to the negative terminal of the source of potential, a second inductance, electromagnetically coupled to said first inductance, connected between the screen electrode and the source of negative potential, and a resonant circuit connected between the control electrode and the cathode of said tube to maintain the frequency of operation of the oscillator relatively fixed.

7. An oscillator for producing current variations of substantially sawtooth waveform comprising an electron discharge tube having at least a cathode, a control electrode, a screen electrode and an anode, a first inductance connected between the anode of said tube and the positive terminal of a source of potential, the negative terminal of which is connected to a point of iixed potential, means for connecting the cathode of said discharge tube to the point of xed potential, a second inductance connected between the screen electrode and the point of xed potential, said rst and second inductances being electromagnetically coupled, a damping tube connected across said first inductance, means for controlling the conductivity of said damping tube, and a circuit connected between the control electrode and the point of xed potential to control the operating frequency of the oscillator.

8. An oscillator for producing current variations of substantially sawtooth waveform comprising an oscillator tube having at least a cathode, a control electrode, a screen electrode and an anode, iirst and second inductance elements electromagnetically coupled to each other, means for connecting the first inductance between the anode of said oscillator tube and a source of positive potential, means for connecting said second inductance between the screen electrode and a point of jflxedpotential, means 4for connecting the cathode of said oscillator tube to the point of xed potential, a damping tube connected across said second inductance, means to control the transconductance Vof said damping tube, and a resonant' circuit connected `between a control electrode ofthe Voscillator' tube and a point of fixed potentialto stabilize the frequency of operation of theoscillator.

- 9.` A,-deflection generatorfor producing current variations of substantially sawtooth waveform comprising ian' 'oscillator tube having a cathode, a control electrode, a screen electrode and an anode, means for connecting the cathode to -a point of fixed potential, means including anrstinductance for normally maintaining the anode positive with respect to the cathode, means including a second inductance, electromagnetically coupled to said rst inductance, for connecting the screen electrode to the point of fixed potential, a tuned circuit coupled between the control electrode and the cathode of said tube, and means whereby a control potential may be applied to the control electrode of said tube to control, within predetermined limits, the operating frequency of the deection generator.

10. An oscillator for producing current variations of substantially sawtooth waveform comprising an oscillator tube having at least a cathode, a control electrode, a screen electrode and an anode, a first inductance connected between the anode of said tube andthe positive terminal of a source of potential, means for connecting the cathode of said tube to the negative terminal of the source of potential, a second inductance, electromagnetically associated with said i'lrst inductance, connected between the screen electrode and the source of negative potential, a tuned circuit coupled ,between the control electrode and the cathode of said tube to maintain the frequency of operation of the oscillator relatively fixed, and means for altering the direct current potential of the control electrode of the oscillator tube to alter the frequency of operation of the oscillator Within a relatively narrow range included within the resonant frequency band of the tuned circuit.

11. A deflection generator for producing current variations of substantially sawtooth waveform comprising an oscillator tube having at least a cathode, a control electrode, a screen electrode and an anode, a first inductance connected between the anode and the positive terminal of a source of potential, means for connecting the cathode to the negativ-e terminal of the source of potential, a second inductance, means for connecting said second inductance between said screen electrode and the negative terminal of the source of potential, said rst and second inductances being electromagnetically coupled, a resonant circuit coupled between the control electrode and the cathode of said tube to stabilize the frequency of operation of the deflection generator, and means whereby synchronizing impulses may be applied to the control electrode of said tube to furtherA control the frequency of operation of the deflection tube.

12. An oscillator for producing current variations of substantially sawtooth waveform comprising an oscillator tube having at least a cathode, a control electrode, a screen electrode and an anode, a first inductance connected between the anode of said tube and the positive terminal of a source of potential, means for connecting the cathode of said tube to the negative terminal of 1l 12 the source of potential, a second inductance, elec- UNITED STATES PATENTS tromagnetically associated with said rst inductance, connected between the screen electrode and Nzugess Farath N B11361936 the source of negative potential, a resonant circuit 2147114 Stockser in WM 1939 coupled between the control electrode and the 5 2255403 Wheeler Se 't 9 1941 cathode of said tube to maintain the frequency 2280733 Tolson AEI; 21 1942 of operation of the oscillator relatively fixed, and 2360697 Lyman "opt '17 1944 means adapted for applying synchronizing irn- 2373165 Ca ein Ac 10 1945 pulses to the control electrode of the oscillator W pr' tube to further control the frequency of operation 10 FOREIGN PATENTS of the oscillator. Nmber Country Date GEORGE C- SZIKLAI- 40,069 Netherlands Feb.15,193'z REFERENCES CITED The following references are of record in the 15 le of this patent: 

